This invention relates to plastic mold equipment, and in particular to a knockout for ejecting molded parts from a plastic mold.
In injection molding, molten plastic is injected into a mold comprising two parts, a cavity and a core. The cavity and core join at a parting line, and when a part has been molded, the mold halves are separated at the parting line to allow ejection of the molded part. Typically, ejection is by means of one or more knockout pins formed in the mold and activated as the mold is opened.
One problem with using ejecting pins is the fact that the pins concentrate ejecting force only locally on the molded part where the part is contacted. Thus, uneven pressure is applied to the molded part. In addition, as a part is being separated from the mold half to which it is adhering, often a partial vacuum is created during the separation until air can rush into any gap to relieve the vacuum. The creation of a vacuum is an undesirable aspect of ejection of a molded part.
The present invention overcomes these detriments of the prior art and others. Not only is the creation of a vacuum avoided, but also by utilization of both air and mechanical force, the part is ejected far more easily and with far less opportunity for damage to the freshly-molded part.